Orthodontics can produce an amazing smile transformation. With today’s advanced appliances and techniques even the most difficult malocclusions (bad bites) can be overcome. All of this innovation, however, depends on one basic anatomical fact: though firmly set in the mouth, our teeth can still move.

Teeth are actually held in place by the periodontal ligament, a strong, elastic tissue that attaches to them through tiny collagen fibers on one side of the ligament and to the jawbone with similar fibers on the other side. When pressure is placed against a tooth, the bone on the opposite side of the force begins to dissolve (resorb), allowing the tooth to move. As it moves, new bone is built up behind the tooth, to stabilize it. Orthodontists take advantage of this natural mechanism through orthodontic hardware like braces that applies pressure in the desired direction of movement, while the ligament and bone do the rest.

There is, though, a downside to this process. The teeth, bone and gum tissues can contain a kind of “memory” for the former natural position of the teeth. Over time, the lower front teeth tend to take a gradual migratory movement back towards their original position. Also, as we age the lower front teeth may crowd each other as there is a genetic influence for teeth to move to the midline of the face, causing a pressure that allows the skinny lower front teeth to slip behind each other. As a result of both of these tendencies, corrected teeth may retreat from their new positions.

To stop these tendencies, we use an appliance known as a retainer after braces or other hardware is removed. As the name implies, this appliance “retains” the teeth in their new position. For structural “memory,” the retainer will keep the teeth in their new position until the impulse to return to the old one has faded, about eighteen months. Retainers can also slow or stop the natural genetic influence of movement, but it may mean wearing a retainer for an indefinite period, especially individuals who’ve undergone orthodontic treatment later in life.

The length of time you’ll need to wear a retainer after braces — and what type, whether a removable appliance or one permanently attached — will depend on a number of factors including the type of malocclusion, your individual mouth structure and age. We’ll recommend the best option that ensures the best chance of keeping your teeth in their new position.